From bd67959f3ad5049c35af0a0e2f8f1a1e60577a49 Mon Sep 17 00:00:00 2001 From: Rich Felker Date: Fri, 6 Mar 2015 13:27:08 -0500 Subject: fix over-alignment of TLS, insufficient builtin TLS on 64-bit archs a conservative estimate of 4*sizeof(size_t) was used as the minimum alignment for thread-local storage, despite the only requirements being alignment suitable for struct pthread and void* (which struct pthread already contains). additional alignment required by the application or libraries is encoded in their headers and is already applied. over-alignment prevented the builtin_tls array from ever being used in dynamic-linked programs on 64-bit archs, thereby requiring allocation at startup even in programs with no TLS of their own. --- src/env/__init_tls.c | 10 ++++++++-- src/ldso/dynlink.c | 10 ++++++++-- 2 files changed, 16 insertions(+), 4 deletions(-) (limited to 'src') diff --git a/src/env/__init_tls.c b/src/env/__init_tls.c index ddc2a736..b0dad429 100644 --- a/src/env/__init_tls.c +++ b/src/env/__init_tls.c @@ -2,6 +2,7 @@ #include #include #include +#include #include "pthread_impl.h" #include "libc.h" #include "atomic.h" @@ -22,7 +23,12 @@ int __init_tp(void *p) #ifndef SHARED -static long long builtin_tls[(sizeof(struct pthread) + 64)/sizeof(long long)]; +static struct builtin_tls { + char c; + struct pthread pt; + void *space[16]; +} builtin_tls[1]; +#define MIN_TLS_ALIGN offsetof(struct builtin_tls, pt) struct tls_image { void *image; @@ -86,7 +92,7 @@ void __init_tls(size_t *aux) } T.size += (-T.size - (uintptr_t)T.image) & (T.align-1); - if (T.align < 4*sizeof(size_t)) T.align = 4*sizeof(size_t); + if (T.align < MIN_TLS_ALIGN) T.align = MIN_TLS_ALIGN; libc.tls_size = 2*sizeof(void *)+T.size+T.align+sizeof(struct pthread); diff --git a/src/ldso/dynlink.c b/src/ldso/dynlink.c index 0bdc988c..ca101993 100644 --- a/src/ldso/dynlink.c +++ b/src/ldso/dynlink.c @@ -122,6 +122,13 @@ void __init_libc(char **, char *); const char *__libc_get_version(void); +static struct builtin_tls { + char c; + struct pthread pt; + void *space[16]; +} builtin_tls[1]; +#define MIN_TLS_ALIGN offsetof(struct builtin_tls, pt) + static struct dso *head, *tail, *ldso, *fini_head; static char *env_path, *sys_path; static unsigned long long gencnt; @@ -132,10 +139,9 @@ static int noload; static jmp_buf *rtld_fail; static pthread_rwlock_t lock; static struct debug debug; -static size_t tls_cnt, tls_offset, tls_align = 4*sizeof(size_t); +static size_t tls_cnt, tls_offset, tls_align = MIN_TLS_ALIGN; static size_t static_tls_cnt; static pthread_mutex_t init_fini_lock = { ._m_type = PTHREAD_MUTEX_RECURSIVE }; -static long long builtin_tls[(sizeof(struct pthread) + 64)/sizeof(long long)]; struct debug *_dl_debug_addr = &debug; -- cgit v1.2.1